1. Field of the Invention
The present invention relates to an object, a method, or a manufacturing method. In addition, the present invention relates to a process, a machine, manufacture, or a composition of matter. In addition, an embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a memory device, a driving method thereof, or a manufacturing method thereof. In particular, one embodiment of the present invention relates to a semiconductor device, a display device, or a light-emitting device each including an oxide semiconductor.
In this specification and the like, a semiconductor device generally means a device that can function by utilizing semiconductor characteristics. A display device, an electro-optical device, a semiconductor circuit, and an electronic device include a semiconductor device in some cases.
2. Description of the Related Art
In recent years, while a transistor is required to be miniaturized with an increase in the degree of integration of integrated circuits (ICs), problems of a decrease in on-state current due to parasitic resistance or deterioration of subthreshold characteristics become significant as the transistor is further miniaturized. In order to solve the above problems, a transistor mainly including silicon has been proposed as a transistor in which a semiconductor is processed to three-dimensional shape called “fin”, whose top surface and side surface are surrounded by a gate electrode (Non-Patent Document 1 and Non-Patent Document 2).
Alternatively, an oxide semiconductor has attracted attention as a semiconductor which can be applied to a transistor. A transistor including an oxide semiconductor can be manufactured easily and operate at higher speed than a transistor including amorphous silicon, and leakage current in the off state is extremely low; thus, the transistor is expected to be applied to an integrated circuit or an image display device (also simply referred to as a display device).
Though it is known that oxygen vacancies in the oxide semiconductor film or the interface cause variation in electric characteristics of the transistor, the problem can be solved by effectively supplying oxygen to the oxide semiconductor film or the interface. As the methods for supplying oxygen to the oxide semiconductor, a method for supplying oxygen from an insulator in contact with the oxide semiconductor (Patent Document 1), and a method for supplying oxygen from a gate electrode (Patent Document 2) are disclosed.